Beater mill having improved beater arm support



April 30, 1968 H. WElSPFENNlNG 3,380,672

BEATER MILL HAVING IMPROVED B EATER ARM SUPPORT Filed D80. 6, 1965 2 Sheets-Sheet 1 HELMUT WEISPFENNING INVENTOR.

BY %km%/ AGENT April 30, 1968 H. WEISPFENNING 3,380,672

BEATER MILL HAVING IMPROVED HEATER ARM SUPPORT Filed Dec. 6. 1965 2 Sheets-Sheet 2 FIG. 7

INNR.

AGENT 'HELMUT WEI F NING United States Patent Claims. c1.241 1s4 ABSTRACT OF THE DISCLOSURE A beater arm support for a plurality of beater arm pairs, each pair having identical oppositely and radially extending beater arms which are mutually supporting. Radially and longitudinally extending slots for receiving the beater arms, and spacers between two beater arm pairs of a shape to accommodate a bore interiorly of the slots.

The invention relates to a beater mill as employed, for example, in the grinding of coal, and is more particularly concerned with a novel manner of supporting the rotating beater elements of such a mill.

It is well known in connection with pulverized coal fired furnaces to make use of beater mills having a beater wheel rotating on a cantilever supported shaft within a mill housing. The coal to be pulverized is fed into the housing in an axial direction with respect to the shaft. Before entering the final pulverization zone, however, the coal first passes through a so-called pre-crusher which is equipped with rotating and exchangeable beater arms.

The present invention is concerned with an advantageous design of the pre-crusher. In this design the beater arms are supported in radially extending slots penetrating the beater arm holder with identical beater elements being formed on opposite sides thereof. In the operation of the mill one end of the one beater arm accordingly serves as an anchor support for the end of another beater arm. The beater holder accordingly is relieved of carrying any substantial load due to centrifugal forces. The dimensions and the weight of the beater arm holder can, therefore, be reduced to such an extent that the beater arm holder offers only a relatively small flow resistance to the stream of coal and carrier gas passing thereover in entering the beater wheel. The beater arms and heater arm holder accordingly represent only a relatively minor additional load which would be imposed on the cantilever shaft and the bearing thereof. This permits the addition of a pre-crusher of the herein disclosed inventive design to existing mills, which originally were not designed for the additional load.

A further advantage of the invention consists in that only simple devices are necessary for attaching the beater arms to the beater arm holder, especially since these de vices serve as anchors not only for one but for two beater arms. Finally, the inventive design permits the use of inexpensive standard rolled bar sections in the fabrication of the beater arms.

It is accordingly a primary object of the invention to provide in a cantilever beater mill a pre-crushing device of an improved design including a pair of beater arms which mutually support themselves as far as centrifugal forces are concerned.

It is another object of the invention to substantially reduce the size and weight of the beater arm holder assembly such that it offers only a minor flow resistance to the stream of working material and permits the ready mounting thereof on mills already in operation.

An additional object of the invention is the provision of a pre-crusher design of exceptionally simple and in- 3,380,672. Patented Apr. 30, 1968 expensive construction, which permits the use of standard simple steel profiles in the construction of the beater arms.

Other objects and advantages of the invention will become apparent from the following description of an illustrative embodiment thereof when taken in conjunction with the accompanying drawings wherein:

FIG. 1A is a diagrammatic representation of a beater mill having a cantilever supported beater wheel;

FIG. 1 is a longitudinal section through the free end of the cantilever shaft of the beater mill and the beater arm holder attached thereto;

FIG. 2 is a partial cross section and end view of the beater arm holder when taken on line 2-2 of FIG. 1;

FIG. 3 is a plan view of the beater arm holder when taken on line 3-3 of FIG. 1;

FIG. 4 is a longitudinal section through the beater arm holder similar to FIG. 1, however, showing beater arms with different support structure;

FIG. 5 is a partial cross section through the beater arm holder when taken on line 55 of FIG. 4;

FIG. 6 is a longitudinal section through the beater arm holder similar to FIG. 4, however, having beater arms with still another different support structure;

FIG. 7 is a partial cross section through the beater arm holder when taken on line 77 of FIG. 6; and

FIG. 8 shows a front view of a beater arm holder being divided into six segments instead of four as are those of FIGS. 1 through 7.

Referring now to the drawings, wherein like referenc characters are used throughout to designate like elements, the illustrative embodiments of the invention depicted therein include a beater mill B as shown in FIG. 1A, having a beater wheel W rotating within a mill housing H and mounted on a mill shaft S which is driven by a motor M. The material to be pulverized together with the carrier gas or air enters the mill housing H axially by way of inlet duct D. A pre-crusher assembly 10 is mounted on the free end of cantilever shaft S. This assembly as shown in larger scale in FIG. 1 comprises a beater wheel holder 11 carried on the end 12 of mill shaft S by means of a threaded socket 13 and/or having a flange 14 bolted to a flange 15 that is keyed to shaft 12 by means of key 16.

In accordance with the invention the free end of holder 11 is provided with two radial slots which, in the preferred embodiment, divide the front part of holder 11 into four segments 19 a shown in FIG. 2. The slots 18 extend longitudinally from the end of the holder 11 to flange 20. Obviously more than two slots could be used, such as three, which would divide the holder 11 into six segments, as shown in FIG. 8.

Slots 18 are so dimensioned that a beater arm element can snugly be inserted therein, with the beater arm element forming a pair of beater arm 22. Preferably standard bar stock is used for the beater arm element which stock can be of rectangular or other cross section, such as circular. The ends of beater arms 22 can be provided with beater plates or heads 23 as shown in FIG. 1A. In the preferred embodiment each beater arm is spaced from the adjacent one, and is provided With a hole 24 at the center thereof for axially receiving one or several pins 25. At selected intervals there is inserted between two beater arm pairs a spacer 26. A plate or cover 28 terminates the beater arm assembly and is attached to the beater arm holder 11 by means of studs 30. A central projection 32 carries a Washer 34 which is dimensioned to prevent turning of studs 30, with the washer in turn being secured by cotter pin 36.

In the embodiment of FIGS. 4 and 5 the beater arms 40 are at the center thereof provided with protuberances 42 which protrude into the laterally aligned slots 18. Thus beater arms 40 are anchored in beater arm holder 11 by 3 means of protuberances 42, instead of by means of pins 25, as are beater arms 22 of FIGS. 1 and 2.

In the embodiment of FIGS. 6 and 7 two adjacent beater arm pairs are fastened to each other by means of a rabbet joint. Thus the beater arms 44 and 46 are provided with opposing matching slots, the slot in arm 4-!- serving to anchor arm 46, and the slot in arm 46 serving to anchor arm 4-4. Each slot may be cut to any suitable depth, such as one-half of the thickness of the arm, as shown in arms 44 and 46, or one-third of the thickness of the arm as shown in arms 48 and St).

The spacers 26 inserted between beater arm pairs can be of any suitable shape such as cylindrical or square. However, it is desirable that they are of such a size that a portion thereof projects into each slot 18 as indicated in FIG. 7. Furthermore, a cylindrical shield or cover 52 is provided having cut-outs accommodating the beater arms projecting therethrough. This outer cover 52 serves the purpose of preventing coal particles from filling the open spaces of slots 18.

While the invention is hereinabove described as being mounted on the end of the mill shaft, the invention is also applicable to pre-crusher assemblies which are mounted on a separate cantilever shaft, independently of the mill shaft which carries the beater wheel. In each case, in addition to the advantages earlier herein set forth the invention permits a quick and easy exchange of beater arms. This is especially true since the beater arm pairs, including the beater plates or heads, can be balanced beforehand and before they are used as replacements for worn out beater arms.

While I have illustrated and described a preferred embodiment of my invention, it is to be understood that such is merely illustrative and not restrictive and that variations and modifications may be made therein without departing from the spirit and scope of the invention. I therefore do not wish to be limited to the precise details set forth but desire to avail myself of such changes as fall Within the purview of my invention.

1 claim:

1. A beater mill having a heater wheel mounted on a rotating shaft supported in a cantilever fashion, means for delivering into said wheel in axial direction a mixture of carrier gas and the material to be pulverized, a shaftmounted pre-crusher through which the material passes before entering the beater wheel, said pre-crusher having a plurality of exchangeable beater arm pairs, with at least two pairs thereof being spaced in axial and circumferential direction, each pair comprising two radially and oppositely extending beater arms being identical and mutually supporting; means for forming radially and longitudinally extending slot means for receiving said opposite beater arms therein, including a bore formed interiorly of the slot means; and longitudinally arranged spacer means between two beater arm pairs, which spacer means are of a shape to accommodate said bore interiorly of said slot means.

2. A beater mill as defined in claim 1 having means forming axially extending opening means in the center portion of each of said pair of beater arms, and pin means passing through said opening means.

3. A beater mill as defined in claim 1, with said heater arm pairs being provided at the central portion thereof with a protrusion lying in a radially extending plane for engagement with a slot circumferentially spaced from each said heater arm pair.

4. A beater mill as defined in claim 1 with each mutually adjacent beater arm pair being provided with matching locking means to provide mutual support.

5. A beater mill as defined in claim 4 in which said matching locking means comprise depressions in each beater arm pair for mating engagement with the adjacent beater arm pair.

References Cited UNITED STATES PATENTS 1,527,818 2/1925 ONeill 241-191 X 1,646,720 10/1927 Andrews 241 154 X 1,713,507 5/1929 Ammon 241 191 X 1,719,831 7/1929 Daniels 241 1s4 1,748,046 2/1930 Bullock 241 191 X 1,977,501 10/1934 Townsend 241 154 X 2,424,316 7/1947 Johnston 241 154 X 2,974,888 3/1961 Everett 241-191 HARRISON L. HINSON, Primary Examiner. 

